Suction cup magnets for temporary attachments

Sometimes you just need a magnet to temporarily hang something up. This is when suction cup magnets that can be used on all smooth surfaces (storefront window, tiles in kitchen and bathroom, non-magnetic fridge door, etc.) come in handy.
The advantage of suction cups is that you can attach them to vertical and horizontal surfaces without having to drill any holes or use glue, for instance on the chrome steel frame of the fan above the stove where you normally can't hang anything up.
Another advantage: The magnet does not leave any scratches on the smooth surface and the suction cup can be removed quickly and without residue.
Please note:

Surface requirements for suction cups: The area needs to be completely smooth and clean (free of grease and dust) before you attach the suction cup, which also has to be free of dirt.

The embedded magnets will start to rust at some point in a damp environment such as a kitchen or bathroom, which means you may have to replace them.

Don't attach too heavy or breakable objects on a mobile magnet because the suction cups may not be strong enough. When the suction cup comes off and the item on it falls, it may damage the counter or floor below. Most suitable are lightweight metal signs or boards that are displayed in a storefront window. In that case, it wouldn't be so bad if a suction cup came off.